Many audio amplifier circuits are known. However, output from such devices typically suffers to a greater or lesser degree from instability in the biasing of the output stages and/or distortion arising from imperfections in the DC power supply for the power amplifier stage.
Further, in many amplifier circuits, either no provision is made for coping with overload conditions (either by way of high amplitude inputs and/or by way of very low impedance between the output(s) and common). Where provision is made, the protection is frequently of the "after the event" type wherein damaging levels of current, voltage or temperature are reached before the protection operates.
It is an object of the present invention to overcome, or substantially ameliorate, the abovementioned disadvantages.